I have an 8830 from verizon.

Are you on BIS or BES? You can't using the re-director. You highlight the [attachement] and press Menu>Open Attachment.

what is BIS or BES

Wirelessly posted (BlackBerry8100/4.2.1 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/102)

BES is used if you connect your device to your corporate server at work. BIS is the standard Internet plan for a standalone BlackBerry from your cell phone carrier. If you have to ask that question you are most likely BIS.
That is what I use. To open attachment (BIS) just open the email, scroll down to where it says [attachments] then click. It should upen up a list of available attachments. Keep in mind BIS can only open attachments for formats IT knows about. You won't be able to open .rar files for example because BIS won't work with it. Mostly the MS Office formats, PDF, picture, and other media can be opened.

I hope this helps you.